GUIDE TO THE COSMOS
BBC
GUIDE TO THE COSMOS
  • BBC FOCUS
  • 승인 2019.05.14 01:05
  • 조회수 182
  • 댓글 0
이 기사를 공유합니다

About this series

In this exclusive four-part series, physicists Jeff Forshaw and Brian Cox introduce us to the biggest ideas in modern physics and cosmology. What is the nature of time? What is everything made from? What happened before the Big Bang, and how will the Universe end? We’ll delve into the deepest questions concerning the very essence of space, time, matter, and reality itself…

Time does not tick at a steady rate across the Universe – in some places it ticks faster 

 

 

this is the ‘twin paradox’, where an astronaut departs from Earth, leaving her twin brother behind. She zips around for a bit in her super-fast spaceship and then lands back on Earth a year later, only to find that many more years have passed back home, and her brother is now an old man. This is exactly the kind of  weirdness that must be true if Einstein is right – though we aren’t aware of it in our everyday lives because we can’t zip around fast enough, and so are tricked into thinking time is more constant than it actually is. The fact that a moving clock does not tick as fast as a stationary one is actually quite easy to demonstrate. First, imagine a clock made from two parallel mirrors, between which a particle of light or ‘photon’ bounces  back and forth (see ‘The key idea’, right). Imagine you have one of these little clocks in your hand, and that you can watch the particle as it goes up and down, counting the bounces as a way of measuring time. Now imagine that a  friend also has one of these clocks, but that she’s moving horizontally. From your point of view, her photon traces out two sides of a triangle as it bounces from one mirror to the other and back again, travelling further during each round trip than the photon in your clock. There’s nothing controversial in what we just said. Here comes the  weird bit. Because, according to Einstein, the light bouncing in your friend’s clock is travelling at the same speed as the light in your clock, the light in your friend’s clock must take longer to bounce between the mirrors. In other words, your friend’s clock is running slower than yours. This remarkable  conclusion might sound like a special feature of light clocks. But it isn’t… it is a feature of all clocks. To understand why, we need to introduce Einstein’s second crucial idea – an idea first introduced by Galileo Galilei in the early 1600s.

본 기사는 유료회원용 기사입니다.
로그인 및 구독신청 후 이용해주세요.


댓글삭제
삭제한 댓글은 다시 복구할 수 없습니다.
그래도 삭제하시겠습니까?
댓글 0
댓글쓰기
계정을 선택하시면 로그인·계정인증을 통해
댓글을 남기실 수 있습니다.

  • 충청남도 보령시 큰오랏3길
  • 법인명 : 이웃집과학자 주식회사
  • 제호 : 이웃집과학자
  • 청소년보호책임자 : 정병진
  • 등록번호 : 보령 바 00002
  • 등록일 : 2016-02-12
  • 발행일 : 2016-02-12
  • 발행인 : 김정환
  • 편집인 : 정병진
  • 이웃집과학자 모든 콘텐츠(영상,기사, 사진)는 저작권법의 보호를 받은바, 무단 전재와 복사, 배포 등을 금합니다.
  • Copyright © 2016-2019 이웃집과학자. All rights reserved. mail to contact@scientist.town
ND소프트